1. Field of the Invention
The present invention relates to a liquid-level detecting structure for detecting a minium level of a liquid accommodated in a tank such as a washer tank.
2. Description of the Related Art
A level warning switch for detecting a remaining amount (minimum level) of a liquid accommodated in a tank (such as a washer in a washer tank and a radiator liquid) is known.
In a conventional level warning switch, a float which moves vertically due to a change in the liquid level is disposed in a cylindrical case. A magnet is secured to a lower surface of the float, and a reed switch is disposed at a lower portion of the case in facing relationship with the magnet. The arrangement provided is such that as the float moves downward due to the change in the liquid level and the magnet is consequently brought to a predetermined position close to the reed switch, the reed switch is turned on for detecting the minimum liquid level, which in turn causes a warning lamp to light up.
With such a conventional level warning switch, when the remaining amount of the liquid in the tank is close to the minimum level and a large acceleration G is produced due to a sudden acceleration or deceleration of a vehicle or high-speed turning thereof, the liquid in the tank moves and the liquid level is inclined. Consequently, the float moves together with the liquid level, causing abnormal turning on and off (so-called chattering) of the reed switch. This causes, for instance, a "flickering" of the warning lamp wherein the warning lamp repeatedly turns on and off within a short time. Accordingly, it has been impossible with the conventional arrangement to sufficiently demonstrate the essential function of giving a warning to the vehicle occupant.
Accordingly, in order to overcome this drawback, a measure, among others, has been adopted in which a timer is provided in a detection circuit of a level warning switch, such that a temporary change in the liquid level, when detected by the level warning switch, is corrected by a control circuit, thereby eliminating the misalarming of the warning lamp, i.e., the so-called "flickering" of the warning lamp in which the turning on and off of the lamp is repeated.
With such a conventional measure, however, the production cost of the level warning system has been inevitably high due to the detection circuit and the like using a timer.